Glutamate metabolism in HIV-infected macrophages: implications for the CNS

2006 ◽  
Vol 291 (4) ◽  
pp. C618-C626 ◽  
Author(s):  
Fabrice Porcheray ◽  
Cathie Léone ◽  
Boubekeur Samah ◽  
Anne-Cécile Rimaniol ◽  
Nathalie Dereuddre-Bosquet ◽  
...  
Keyword(s):  
Gene Expression ◽  
Glutamine Synthetase ◽  
Hiv Infection ◽  
Excitatory Amino Acid ◽  
Glutamate Uptake ◽  
Glutamate Transport ◽  
Activated Macrophages ◽  
Glutamate Metabolism ◽  
Excitatory Amino Acid Transporter ◽  
Hiv Encephalitis

Central nervous system disorders are still a common complication of human immunodeficiency virus (HIV) infection and can lead to dementia and death. They are mostly the consequences of an inflammatory macrophagic activation and relate to glutamate-mediated excitotoxicity. However, recent studies also suggest neuroprotective aspects of macrophage activation through the expression of glutamate transporters and glutamine synthetase. We thus aimed to study whether HIV infection or activation of macrophages could modulate glutamate metabolism in these cells. We assessed the effect of HIV infection on glutamate transporter expression as well as on glutamate uptake by macrophages and showed that glutamate transport was partially decreased in the course of virus replication, whereas excitatory amino acid transporter-2 (EAAT-2) gene expression was dramatically increased. The consequences of HIV infection on glutamine synthetase were also measured and for the first time we show the functional expression of this key enzyme in macrophages. This expression was repressed during virus production. We then quantified EAAT-1 and EAAT-2 gene expression as well as glutamate uptake in differentially activated macrophages and show that the effects of HIV are not directly related to pro- or anti-inflammatory mediators. Finally, this study shows that glutamate transport by macrophages is less affected than what has been described in astrocytes. Macrophages may thus play a role in neuroprotection against glutamate in the infected brain, through their expression of both EAATs and glutamine synthetase. Because glutamate metabolism by activated macrophages is sensitive to both HIV infection and inflammation, it may thus be of potential interest as a therapeutic target in HIV encephalitis.

Elevated ammonium levels: differential acute effects on three glutamate transporter isoforms

2012 ◽  
Vol 302 (6) ◽  
pp. C880-C891 ◽  
Author(s):  
Rikke Søgaard ◽  
Ivana Novak ◽  
Nanna MacAulay
Keyword(s):  
Excitatory Amino Acid ◽  
Glutamate Uptake ◽  
Brain Slices ◽  
Glutamate Transporter ◽  
Surface Expression ◽  
Glutamate Transport ◽  
Excitatory Amino Acid Transporter ◽  
Ph Buffering ◽  
Specific Effects ◽  
Intracellular Alkalinization

Increased ammonium (NH4+/NH3) in the brain is a significant factor in the pathophysiology of hepatic encephalopathy, which involves altered glutamatergic neurotransmission. In glial cell cultures and brain slices, glutamate uptake either decreases or increases following acute ammonium exposure but the factors responsible for the opposing effects are unknown. Excitatory amino acid transporter isoforms EAAT1, EAAT2, and EAAT3 were expressed in Xenopus oocytes to study effects of ammonium exposure on their individual function. Ammonium increased EAAT1- and EAAT3-mediated [3H]glutamate uptake and glutamate transport currents but had no effect on EAAT2. The maximal EAAT3-mediated glutamate transport current was increased but the apparent affinities for glutamate and Na+ were unaltered. Ammonium did not affect EAAT3-mediated transient currents, indicating that EAAT3 surface expression was not enhanced. The ammonium-induced stimulation of EAAT3 increased with increasing extracellular pH, suggesting that the gaseous form NH3 mediates the effect. An ammonium-induced intracellular alkalinization was excluded as the cause of the enhanced EAAT3 activity because 1) ammonium acidified the oocyte cytoplasm, 2) intracellular pH buffering with MOPS did not reduce the stimulation, and 3) ammonium enhanced pH-independent cysteine transport. Our data suggest that the ammonium-elicited uptake stimulation is not caused by intracellular alkalinization or changes in the concentrations of cotransported ions but may be due to a direct effect on EAAT1/EAAT3. We predict that EAAT isoform-specific effects of ammonium combined with cell-specific differences in EAAT isoform expression may explain the conflicting reports on ammonium-induced changes in glial glutamate uptake.

EAAT1 is involved in transport ofl-glutamate during differentiation of the Caco-2 cell line

2000 ◽  
Vol 279 (2) ◽  
pp. G366-G373 ◽  
Author(s):  
Agnès Mordrelle ◽  
Eric Jullian ◽  
Cyrille Costa ◽  
Estelle Cormet-Boyaka ◽  
Robert Benamouzig ◽  
...  
Keyword(s):  
Amino Acid ◽  
Cell Line ◽  
Excitatory Amino Acid ◽  
Kinetic Studies ◽  
Glutamate Transport ◽  
Hill Coefficient ◽  
Amino Acid Transporters ◽  
Intestinal Epithelial ◽  
Transport Capacity ◽  
Excitatory Amino Acid Transporter

Little is known concerning the expression of amino acid transporters during intestinal epithelial cell differentiation. The transport mechanism ofl-glutamate and its regulation during the differentiation process were investigated using the human intestinal Caco-2 cell line. Kinetic studies demonstrated the presence of a single, high-affinity,d-aspartate-sensitive l-glutamate transport system in both confluent and fully differentiated Caco-2 cells. This transport was clearly Na+ dependent, with a Hill coefficient of 2.9 ± 0.3, suggesting a 3 Na+-to-1 glutamate stoichiometry and corresponding to the well-characterized XA,G − system. The excitatory amino acid transporter (EAAT)1 transcript was consistently expressed in the Caco-2 cell line, whereas the epithelial and neuronal EAAT3 transporter was barely detected. In contrast with systems B0 and y+, which have previously been reported to be downregulated when Caco-2 cells stop proliferating, l-glutamate transport capacity was found to increase steadily between day 8 and day 17. This increase was correlated with the level of EAAT1 mRNA, which might reflect an increase in EAAT1 gene transcription and/or stabilization of the EAAT1 transcript.

scholarly journals Abnormalities in Glutamate Metabolism and Excitotoxicity in the Retinal Diseases

Scientifica ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Makoto Ishikawa
Keyword(s):  
Glutamine Synthetase ◽  
Physiological Condition ◽  
Glutamate Uptake ◽  
Glutamate Transporters ◽  
Retinal Diseases ◽  
Glutamate Metabolism ◽  
Retinal Neurons ◽  
Major Pathway ◽  
Excitatory Neurotransmitter ◽  
Pathological Conditions

In the physiological condition, glutamate acts as an excitatory neurotransmitter in the retina. However, excessive glutamate can be toxic to retinal neurons by overstimulation of the glutamate receptors. Glutamate excess is primarily attributed to perturbation in the homeostasis of the glutamate metabolism. Major pathway of glutamate metabolism consists of glutamate uptake by glutamate transporters followed by enzymatic conversion of glutamate to nontoxic glutamine by glutamine synthetase. Glutamate metabolism requires energy supply, and the energy loss inhibits the functions of both glutamate transporters and glutamine synthetase. In this review, we describe the present knowledge concerning the retinal glutamate metabolism under the physiological and pathological conditions.

Introduction: Glutamate transport, metabolism, and physiological responses

1999 ◽  
Vol 277 (4) ◽  
pp. F477-F480 ◽  
Author(s):  
M. A. Hediger ◽  
T. C. Welbourne
Keyword(s):  
Amino Acid ◽  
San Francisco ◽  
Excitatory Amino Acid ◽  
Glutamate Transport ◽  
Glutamine Metabolism ◽  
Epithelial Cell Line ◽  
Amino Acid Transporters ◽  
Excitatory Amino Acid Transporter ◽  
Renal Epithelial Cell

The material covered in this set of articles was originally presented at Experimental Biology ’98, in San Francisco, CA, on April 20, 1998. Here, the participants recount important elements of current research on the role of glutamate transporter activity in cellular signaling, metabolism, and organ function. W. A. Fairman and S. G. Amara discuss the five subtypes of human excitatory amino acid transporters, with emphasis on the EAAT4 subtype. M. A. Hediger discusses the expression and action of EAAC1 subtype of the human excitatory amino acid transporter. I. Nissim provides an overview of the significant role of pH in regulating Gln/Glu metabolism in the kidney, liver, and brain. J. D. McGivan and B. Nicholson describe some characteristics of glutamate transport regulation with regard to a specific experimental model of the bovine renal epithelial cell line NBL-1. Finally, T. C. Welbourne and J. C. Matthews introduce the “functional unit” concept of glutamate transport and how this relates to both glutamine metabolism and paracellular permeability.

Water and urea permeation pathways of the human excitatory amino acid transporter EAAT1

2011 ◽  
Vol 439 (2) ◽  
pp. 333-340 ◽  
Author(s):  
Robert J. Vandenberg ◽  
Cheryl A. Handford ◽  
Ewan M. Campbell ◽  
Renae M. Ryan ◽  
Andrea J. Yool
Keyword(s):  
Amino Acid ◽  
Water Transport ◽  
Transport Process ◽  
Excitatory Amino Acid ◽  
Anion Channel ◽  
Glutamate Transporters ◽  
Amino Acid Transporter ◽  
Glutamate Transport ◽  
Excitatory Amino Acid Transporter ◽  
Permeation Properties

Glutamate transport is coupled to the co-transport of 3 Na+ and 1 H+ followed by the counter-transport of 1 K+. In addition, glutamate and Na+ binding to glutamate transporters generates an uncoupled anion conductance. The human glial glutamate transporter EAAT1 (excitatory amino acid transporter 1) also allows significant passive and active water transport, which suggests that water permeation through glutamate transporters may play an important role in glial cell homoeostasis. Urea also permeates EAAT1 and has been used to characterize the permeation properties of the transporter. We have previously identified a series of mutations that differentially affect either the glutamate transport process or the substrate-activated channel function of EAAT1. The water and urea permeation properties of wild-type EAAT1 and two mutant transporters were measured to identify which permeation pathway facilitates the movement of these molecules. We demonstrate that there is a significant rate of L-glutamate-stimulated passive and active water transport. Both the passive and active L-glutamate-stimulated water transport is most closely associated with the glutamate transport process. In contrast, L-glutamate-stimulated [14C]urea permeation is associated with the anion channel of the transporter. However, there is also likely to be a transporter-specific, but glutamate independent, flux of water via the anion channel.

scholarly journals Gene expression patterns associated with neurological disease in HIV infection

2016 ◽  
Author(s):  
Pietro Paolo Sanna ◽  
Vez Repunte-Canonigo ◽  
Eliezer Masliah ◽  
Celine Lefebvre
Keyword(s):  
Gene Expression ◽  
White Matter ◽  
Hiv Infection ◽  
Immune Activation ◽  
Tissue Injury ◽  
Expression Profiles ◽  
Expression Patterns ◽  
Distinct Pattern ◽  
Gene Set Enrichment Analysis ◽  
Hiv Encephalitis

AbstractTo provide new insight into the pathogenesis of neurocognitive impairments (NCI) in HIV infection, we used the Gene Set Enrichment Analysis (GSEA) algorithm to analyze pathway dysregulations in gene expression profiles of HIV-infected patients with or without NCI and HIV encephalitis (HIVE). While HIVE was characterized by widespread inflammation and tissue damage, gene expression evidence of induction of interferon (IFN), cytokines and tissue injury was apparent in all brain regions studied before the emergence of NCI. Various degrees of white matter changes were present in all HIV-infected subjects and were the primary manifestation in patients with NCI in the absence of HIVE. The latter showed a distinct pattern of immune activation with induction of chemokines, cytokines, β-defensins, and limited IFN induction.Altogether results indicate that significant neuroinflammation and neuronal suffering precede NCI. Patients with NCI without HIVE showed a predominantly white matter dysfunction with a distinct pattern of immune activation.

scholarly journals Ceftriaxone Treatment Affects EAAT2 Expression and Glutamatergic Neurotransmission and Exerts a Weak Anticonvulsant Effect in Young Rats

2019 ◽  
Vol 20 (23) ◽  
pp. 5852 ◽  
Author(s):  
Zaitsev ◽  
Malkin ◽  
Postnikova ◽  
Smolensky ◽  
Zubareva ◽  
...  
Keyword(s):  
Excitatory Amino Acid ◽  
Glutamate Uptake ◽  
Temporal Cortex ◽  
Young Male ◽  
Anticonvulsant Effect ◽  
Maximal Electroshock ◽  
Glutamatergic Neurotransmission ◽  
Excitatory Amino Acid Transporter ◽  
Young Rats ◽  
Wide Range

Epilepsy is a common neurological disorder. Despite the availability of a wide range of antiepileptic drugs, these are unsuccessful in preventing seizures in 20–30% of patients. Therefore, new pharmacological strategies are urgently required to control seizures. Modulation of glutamate uptake may have potential in the treatment of pharmacoresistant forms of epilepsy. Previous research showed that the antibiotic ceftriaxone (CTX) increased the expression and functional activity of excitatory amino acid transporter 2 (EAAT2) and exerted considerable anticonvulsant effects. However, other studies did not confirm a significant anticonvulsant effect of CTX administration. We investigated the impacts of CTX treatment on EAAT expression and glutamatergic neurotransmission, as well its anticonvulsant action, in young male Wistar rats. As shown by a quantitative real-time polymerase chain reaction (qPCR) assay and a Western blot analysis, the mRNA but not the protein level of EAAT2 increased in the hippocampus following CTX treatment. Repetitive CTX administration had only a mild anticonvulsant effect on pentylenetetrazol (PTZ)-induced convulsions in a maximal electroshock threshold test (MEST). CTX treatment did not affect the glutamatergic neurotransmission, including synaptic efficacy, short-term facilitation, or the summation of excitatory postsynaptic potentials (EPSPs) in the hippocampus and temporal cortex. However, it decreased the field EPSP (fEPSP) amplitudes evoked by intense electrical stimulation. In conclusion, in young rats, CTX treatment did not induce overexpression of EAAT2, therefore exerting only a weak antiseizure effect. Our data provide new insight into the effects of modulation of EAAT2 expression on brain functioning.

Regulation of mitochondrial glutamine/glutamate metabolism by glutamate transport: studies with 15N

2001 ◽  
Vol 280 (5) ◽  
pp. C1151-C1159 ◽  
Author(s):  
Tomas Welbourne ◽  
Itzhak Nissim
Keyword(s):  
Glutamate Uptake ◽  
Glutamate Transport ◽  
Glutamate Metabolism ◽  
Glutamine Concentration ◽  
Metabolic Fate ◽  
Glutamate Concentration ◽  
Transport Studies ◽  
The Media ◽  
Transport Inhibitors

We focused on the role of plasma membrane glutamate uptake in modulating the intracellular glutaminase (GA) and glutamate dehydrogenase (GDH) flux and in determining the fate of the intracellular glutamate in the proximal tubule-like LLC-PK1-F+ cell line. We used high-affinity glutamate transport inhibitors d-aspartate (d-Asp) and dl-threo-β-hydroxyaspartate (THA) to block extracellular uptake and then used [15N]glutamate or [2-15N]glutamine to follow the metabolic fate and distribution of glutamine and glutamate. In monolayers incubated with [2-15N]glutamine (99 atom %excess), glutamine and glutamate equilibrated throughout the intra- and extracellular compartments. In the presence of 5 mMd-Asp and 0.5 mM THA, glutamine distribution remained unchanged, but the intracellular glutamate enrichment decreased by 33% ( P < 0.05) as the extracellular enrichment increased by 39% ( P < 0.005). With glutamate uptake blocked, intracellular glutamate concentration decreased by 37% ( P < 0.0001), in contrast to intracellular glutamine concentration, which remained unchanged. Both glutamine disappearance from the media and the estimated intracellular GA flux increased with the fall in the intracellular glutamate concentration. The labeled glutamate and NH[Formula: see text] formed from [2-15N]glutamine and recovered in the media increased 12- and 3-fold, respectively, consistent with accelerated GA and GDH flux. However, labeled alanine formation was reduced by 37%, indicating inhibition of transamination. Although both d-Asp and THA alone accelerated the GA and GDH flux, only THA inhibited transamination. These results are consistent with glutamate transport both regulating and being regulated by glutamine and glutamate metabolism in epithelial cells.

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